At this time of year, when public health officials generally warn that the virus is widespread, you either hear flu-related conversations or have them yourself.

Often, they’re variations on something like this:

“Flu season sounds bad this year. Glad I got a flu shot. Did you get one?”

“No.”

“Why not?”

“I got one before and it gave me the flu. Same thing’s happened to friends and other members of my family.”

It’s the kind of conversation that drives Dr. Joe Iser, chief health officer of the Southern Nevada Health District, up the wall.

For years now, in an effort to keep people from being among the 200,000 to 300,000 hospitalized annually from the flu — up to 49,000 die each year — Iser has shared what he knows: It’s scientifically impossible to contract the flu from a flu shot.

He points out flu shots contain only a dead virus, and a dead virus is, well, dead.

(Unlike a zombie, it can’t rise from the dead to hurt you.)

And the nasal vaccine, FluMist, which does contain a live virus, is deliberately engineered to remove the parts of the virus that make people sick.

In December, the Centers for Disease Control and Prevention reported that the flu vaccine kept nearly 80,000 people out of the hospital in 2013 and prevented 6.6 million cases of flu. With a vaccination rate of only 45 percent — thanks largely to the flu shot-flu myth — vaccination still lowered the rate of illness and hospitalization by 17 percent.

Had 70 percent of the population been vaccinated, 4.4 million people would not have gotten sick and 30,000 more would have stayed out of the hospital, federal officials estimate.

So why does this flu myth live on and on?

Well, Iser says, some people mistake the side effects of the vaccine for the flu. Although the most common side effects of a flu shot are soreness, redness and swelling where the shot is given, it is also true that low-grade fever, headache and muscle aches can occur.

The flu shot-flu myth also lives on because there are others who, after receiving a flu shot, get sick with a cold within a few days of receiving the vaccine and mistake it for the flu. They forget flu season just happens to coincide with cold season, when bugs causing colds are in the air. The vaccine, instead of a sneezing co-worker, gets the blame for causing a sickness that shares many similarities with a cold.

Keep in mind, Iser says, that there is a difference between a cold, which usually lasts about a week, and the flu. A cold is a milder respiratory illness, one that usually begins with a sore throat, which goes away after a day or two, followed by nasal symptoms of a runny nose, congestion and cough. There may be a mild fever.

Flu symptoms usually come on quickly and are more severe. Headache, high fever, sore throat, muscle aches and soreness, cough and congestion are usual symptoms. Vomiting and diarrhea are associated with the H1N1 virus, the strain of flu now hitting most of the nation, including Southern Nevada. A common complication of the flu is pneumonia.

Many doctors say the best way to know whether you have cold or flu symptoms is to take your temperature. A cold seldom has fever above 101, but the flu will. Muscle and body aches are also more common with the flu.

Above all else, Iser blames coincidence, coupled with the need for people to see a cause and effect for what happens in life, for perpetuating the flu shot-flu myth.

Nevertheless, he wants people to remember that after you get a flu shot, it takes about two weeks for your body to make enough antibodies to protect you against the flu.

With that in mind, Iser notes there are people who are already infected with the flu virus — it can take from one to seven days to show symptoms — when they get a flu shot. When they come down with the flu a day or two after the vaccination, they blame the shot.

There also are people, Iser says, who will get infected with the flu virus after they get a flu shot but before their bodies have had at least two weeks to make antibodies.

“People want to see a cause and effect for what happens,” Iser says, “but we’re talking about coincidences that have no scientific validity.”

It is important, Iser says, that adults see the flu shot-flu myth for what it is — a myth. That way they can pass on to their children just how important it is to be vaccinated.

I’ve recognized the myth for what it is for years and actually thought I did a pretty good job explaining the importance of flu vaccinations to my children until I received a phone call the other day from Tatiana, my youngest daughter and a college junior honors student in Texas.

“Dad, the doctor said I’ve got the flu,” she moaned. “I’ve been throwing up and everything. I’m so hot.”

“Did you get a flu shot?”

“No.”

“Why not?”

“All my friends said when they got one, they got the flu.”

“Didn’t I explain to you that was a myth, to go ahead and get a flu shot?”